Fluid consumption meter with noise sensor

ABSTRACT

A consumption meter, e.g. a water or heat meter, for measuring a flow rate of a fluid supplied in a flow tube. First and second ultrasonic transducers are arranged at the flow tube for transmitting and receiving ultrasonic signals transmitted through the fluid and operated by a flow measurement sub-circuit for generating a signal indicative of the flow rate of the fluid. A noise measurement sub-circuit operates a sensor arranged at the flow tube for detection of acoustic signals of the flow tube, and being arranged to generate a signal indicative of a noise level of the flow tube accordingly. This sensor may comprise a separate transducer, or the sensor may be constituted by one or both of the first and second ultrasonic transducers. The consumption meter may communicate data representative of the noise level via a communication module along with data consumed amount of water, heat etc. Such consumer noise level measurement at the consumer site allows collection of noise level data to assist in locating fluid leakages in a fluid supply pipe system.

FIELD OF THE INVENTION

The present invention relates to the field of devices with a sensor formeasurement of acoustic noise in a fluid. More specifically, theinvention relates to the field of devices with a noise level sensor formonitoring noise in a utility piping network. Specifically, theinvention provides a noise level sensor integrated with an ultrasonicflow meter, e.g. an ultrasonic consumption meter, or utility meter,comprising an ultrasonic flow meter, for measuring consumption data of asupplied utility, e.g. water, heat, or cooling.

BACKGROUND OF THE INVENTION

In distribution networks for potable water, hot water for districtheating and/or cold water for district cooling, it is important to beable to quickly detect anomalies in day-to-day performance. Forinstance, a busted pipe in a water distribution network can easily causethe loss of hundreds or even thousands of cubic meters of clean, potablewater, resulting in a monetary loss to the distributor as well as anenvironmental loss to the whole community. Another example could be avalve in a district heating distribution network, which does not open orclose fully as intended. As a result, pressure pumps may have to beoperated at a higher revolution rate, causing increased energyconsumption by the distributor and a reduced efficiency of heating atthe consumer site.

Hence, it is desirable to the distributor, and eventually to theconsumer, to aid the distributor in detecting and locating suchanomalies shortly after, or even before, they fully develop.

In the case of pipe leaks or bursts various methods for location exist.One of these involves a number of hydrophones installed on hydrants orin wells. The signals from the hydrophones are correlated in order totriangulate the leak position. Alternatively, tracers may be introducedinto the fluid. Such a tracer could be gas or a fast decayingradioactive substance. Finally, ground radar provides a means to detectthe water accumulation as a result of a (major) leak. Common to thesemethods is that they typically require the involvement of asub-contractor to provide the expertise of handling the sophisticatedequipment needed as well as interpreting the data generated.

SUMMARY OF THE INVENTION

It would be advantageous to provide a simple and low cost device toallow monitoring for leaks in a utility network, hereby allowing utilitycompanies to distribute such devices at several positions in the utilitynetwork.

In a first aspect, the invention provides a consumption meter arrangedto measure a flow rate of a fluid, the consumption meter comprising: aflow tube with a through-going opening for passage of the fluid betweenan inlet and an outlet, first and second ultrasonic transducers arrangedat the flow tube for transmitting and receiving ultrasonic signalstransmitted through the fluid, a control circuit comprising a flowmeasurement sub-circuit arranged for operating the first and secondultrasonic transducers, and being arranged to generate a signalindicative of the flow rate of the fluid from the transmitted andreceived ultrasonic signals transmitted through the fluid, characterisedin that the control circuit further comprises a noise measurementsub-circuit, arranged for generating a signal indicative of a noiselevel of the flow tube or of the fluid therein by means of operating adedicated noise level sensor arranged at the flow tube or by means ofoperating at least one of the first and second ultrasonic transducers todetect acoustic signals of the flow tube or of the fluid.

With the consumption meter of the invention, the noise level of a flowtube per se or of the fluid therein is detected by means of a dedicatednoise level sensor or by means of at least one of the ultrasonictransducers.

Thus, with one embodiment of the invention, a dedicated noise levelsensor is arranged with the consumption meter to detect the said noiselevel. With another embodiment of the invention at least one of thefirst and second ultrasonic transducers, which is otherwise used forflow measurement purposes, is used to detect the said noise level aswell.

Either of the dedicated noise level sensor or the at least one of thefirst and second ultrasonic transducers detects the noise level bydetecting acoustic signals of the flow tuber per se or of the fluidtherein.

According to the invention, the control circuit of the consumption meterhas a flow measurement sub-circuit for operating the first and secondultrasonic transducers in their flow measurement mode. The controlcircuit of the consumption meter also has a noise measurementsub-circuit for operating either of the dedicated noise level sensor orthe at least one of the first and second ultrasonic transducers in theirnoise level measurement mode.

By “control circuit” or “sub-circuit” is understood the necessaryelectronic circuit adapted to control the function of the first andsecond ultrasonic transducers, such as according to known principles oftime-of-flight measurements, and of the dedicated noise level sensor orthe at least one of the first and second ultrasonic transducer for noiselevel detection.

The invention is advantageous in that an ultrasonic consumption meter iscapable of measuring flow rate, e.g. as known in existing water or aheat meters, is also used to measure a noise level of the flow tube orthe fluid therein, i.e. acoustic signals below 2 kHz, i.e. below theultrasonic frequency range. One advantage of the invention is that thenoise level is measured at the position of the consumer site. Eventhough the noise level may vary over time at each site, valuableinformation is still gained, especially if all or most consumptionmeters in a municipal distribution network deliver noise level data tothe distributor. Hereby, a greater picture can be drawn up by the powerof plurality, and anomalies in the distribution network, e.g. leaks inthe piping system, can be more precisely uncovered. If in additiongeographical data are available of the location of the individualconsumption meters, the location of an anomaly can be estimated. Theuncertainty of this location is likely to be reduced by the density ofconsumption meters and the accuracy of their respective positions.

Furthermore, distribution networks with so-called automatic meterreading (AMR) systems are common, in which consumption data are relayedfrom the consumption meters at the consumer site to the distributor withregular time intervals, spanning from hourly to yearly. Typically, dataare transmitted between 1 and 24 times every day. The communicationtypically takes place via a wireless network, which is operated byeither the distributor or a subcontractor, and hence is dedicated to thetask. The capacity of such a communication network suffices to carryadditional information besides the consumption data. Thus, suchadditional information could be data representing the noise level in thefluid distribution pipes from each consumption meter. Hereby, thedistributor can store and/or process such noise level data in adedicated processing system, e.g. for monitoring leaks or otheranomalies in the piping system. The sensitivity of such monitoringsystem may be improved even more by combining noise level data withother data that from each consumer site, such as flow rate, pressure,and temperature. Such data may especially be useful when combined in ahydraulic model for the entire distribution network pipe system.

Studies have shown that acoustic noise due to leaks in pipes is dominantin the frequency range below 2 kHz, depending on the leak size, pipematerial, flow rate and operating pressure. Ultrasonic flow meters aretypically operated in the MHz range, thus the relevant noise levelfrequency range is significantly different from the frequencies used inflow rate measurements. The acoustic signals can be measured in avariety of different ways with different sensors, spanning from a simplemoving coil microphone via capacitive sensors to piezoelectric sensors.Since a consumption meter based on ultrasonic measurement of flowalready comprises ultrasonic transducers, such as piezoelectrictransducers, in one embodiment, the same transducer(s) involved in flowrate measurements is used as sensor to detect acoustic signals relatingto the noise level in the flow tube or the fluid therein. It is to beunderstood, however, that according to the invention the consumptionmeter may also comprise a dedicated noise level sensor for detection ofacoustic signals, such as a third ultrasonic transducer, or a dedicatedsensor based on another sensor technology.

Modern consumption meters employ one or more microcontrollers to performthe flow measurement and to calculate data representing a consumptionamount. Thus, it is to be understood that the flow measurementsub-circuit and the noise measurement sub-circuit may be implemented ina single processor, or in separate processors. The computing power of amodern microcontroller is adequate to perform the data analysis of thesignal recorded by the noise level sensor, e.g. to perform a statisticalanalysis of noise levels sensed over a period of time, thus reducing theamount of data to be transmitted rather than transmitting large numbersof unprocessed data.

Data processing of the output from the sensor may specifically be asimple root-mean-square (RMS) calculation to provide a valuerepresenting a measure of the overall noise level. E.g. in a selectedfrequency band, such as 10-500 Hz. Analysis that is more sophisticatedmay be frequency filtering into certain frequency bands, followed by anRMS calculation, to provide a range of noise figures associated withdifferent frequency bands. Finally, a full Fast Fourier Transform (FFT)could be performed to provide the full spectrum of acoustic signals,involving noise power density as well the associated phase information.The latter level of analysis may be desirable, in order to perform across correlation calculation with the purpose of triangulating thelocation of the noise source. However, for many practical purposes theinformation coming from the simpler noise figure calculation suffice toindicate the position of the noise source.

The data processing on-board the consumption meter may comprisedetecting if a measure of average or peak noise level exceeds apredetermined threshold value. In such case, the consumption meter maybe arranged to transmit a special warning signal of the like. This mayfacilitate processing at the distributor side, since leakages or otheranomalies can be easily monitored by observing such warnings.

In the following, features and embodiments of the invention aredescribed.

According to one embodiment of the invention the noise measurementsub-circuit is arranged for generating the signal indicative of thenoise level of the flow tube or of the fluid therein by means ofoperating the dedicated noise level sensor as well as by operating atleast one of the first and second ultrasonic transducers to detectacoustic signals of the flow tube or of the fluid.

Thus, with this embodiment the noise level is detected by means of atleast one of the first and second ultrasonic transducers, as well as bymeans of a dedicated noise level sensor. Although one of the said meansmay suffice to detect the noise level, such dual noise level detectionallows for more precise determinations, and in particular for a moreprecise distinction of different noise sources, such as to be able toeliminate transient noises such as from traffic and/or continuous ornear-continuous noises such as from heating or cooling systems.

Moreover, the noise measurement sub-circuit may comprise at least onetransimpedance amplifier for the conversion of a current indicative ofthe noise level of the flow tube or of the fluid therein to a voltageindicative of the noise level of the flow tube or the fluid therein.

The use of transimpedance amplifiers with the noise measurementsub-circuit may eliminate electrical noise which does not originate fromthe flow tube or the fluid therein: The very small acoustic signalspicked up by the dedicated noise level sensor or the at least one of thefirst and second ultrasonic transducers may be based on generation ofelectric charge, such as with piezo-electric transducers. The littlecurrents resulting from such generation of charge requires substantialamplification to obtain a useable signal, and it is crucial to suppressother noise sources. This can be achieved by the use of transimpedanceamplifiers, which convert current to voltage and suppress (by notamplifying) voltage noise sources.

The dedicated noise level sensor with the consumption meter according tothe invention may be arranged at an acoustic window of the wall of theflow tube. Arranging the dedicated noise level sensor with an acousticwindow, such as at a position at the wall with a wall thickness adaptedto the sensor, allows for efficient pick-up of acoustic signals from theflow tube or the fluid therein.

The acoustic window is an integrated part of the flow tube wallproviding an unbroken continuous flow tube. Further, the section or areaof the flow tube constituting the acoustic window may be of a thicknessequal to, or smaller or greater than the remainder of the flow tube.

In particular, with such arrangement of the dedicated noise levelsensor, the sensor may be a third ultrasonic transducer. In addition,the dedicated noise level sensor may be arranged along the flow tube ata position between the first and second ultrasonic transducers.

Further to the arrangement of the dedicated noise level sensor, theconsumption meter may comprise a housing and flow tube in the form of amonolithic polymer structure cast in one piece and having a cavity, thecavity accommodating the first and second ultrasonic transducers and thecontrol circuit.

With this embodiment, the consumption meter housing is part of a sharedmonolithic polymer structure having a shared wall between the flow tubeand housing. Such wall is unbroken, i.e. it has no holes between theflow tube and the cavity of the housing. The acoustic window is part ofor integrated in the shared wall. Such structure allows for ease ofmanufacture of the consumption meter structure, and allows for a properarrangement of the dedicated noise level sensor: Within the non-humidenvironment of cavity of the housing, and still in intimate contact withthe flow tube.

Thus, according to an embodiment of the invention the acoustic window isconstituted by a first area of the flow tube wall of reduced thickness,compared to a second area of the flow tube wall adjacent the first area.

With this embodiment, the dedicated noise level sensor is arranged withan area of the flow tube wall, which is interfaced, or even surrounded,by another area with a higher thickness than the area with the sensor.Being manufactured in a proper material such a fiber-reinforced polymer,e.g. fiber-reinforced polyphenylene sulphide (PPS), the thicker areainterfacing the sensor area is less susceptible to mechanicaldeformation from the acoustic signals than is the sensor area, thedeformations thus being concentrated with the sensor area and in turndetected there.

With an alternative embodiment of the invention, the acoustic window isconstituted by a first area of the flow tube wall having a greaterthickness than the second area of the flow tube wall, adjacent to orsurrounding the first area.

With this embodiment, the dedicated noise level sensor is arranged withan area of the flow tube wall, which is interfaced, or even surrounded,by another area with a smaller thickness than the area with the sensor.In this case, the thickness of the sensor area may be dimensionallyadapted to resonate with specific noise frequencies, characteristic ofacoustic noise of the flow tube or the fluid therein.

Alternatively, the dedicated noise level sensor may be arranged with theflow tube wall in an opening of the flow tube wall. Moreover, thededicated noise level sensor may also be arranged in the fluid in theflow tube.

With both of these embodiments, the dedicated noise level sensor is indirect contact with the fluid in flow tube and the acoustic signalstherein. Such arrangements of the dedicated noise level sensor allow foran easy detection of the acoustic signal in the fluid.

Whereas the dedicated noise level sensor may preferably be a thirdultrasonic transducer, such as a piezo-electric sensor, it may as wellbe based on another sensor technology known in the art, such as being acapacitive sensor, an inductive sensor, an optical sensor, or apiezo-resistive sensor, such as a piezo-resistive strain gauge.

With a dedicated noise level sensor it is possible to select a sensorwith improved sensitivity to the specific acoustic frequency range ofinterest, i.e. related to fluid leakage noise.

In embodiments comprising a third ultrasonic transducer to be used assaid dedicated noise level sensor, the third ultrasonic transducer maycomprise a piezoelectric element with a first surface facing the flowtube, and wherein a second surface opposite the first surface of thepiezoelectric element is supported by a rigid backing of an acousticallydampening material, e.g. a dampening material comprising rubber. In thisway, it is possible to provide an improved sensitivity to noise in adesired frequency range.

With an alternative embodiment of the invention, at least one of thefirst and second ultrasonic flow transducers is operated to detect theacoustic signals of the flow tube or of the fluid therein. Inparticular, both of the first and second ultrasonic flow transducers maybe operated to detect the acoustic signals of the flow tube or of thefluid therein. Accordingly with these embodiments, at least one oralternatively both of the ultrasonic flow transducers, which areotherwise used for flow rate measurements, are also used to detect thenoise level of the flow tube or of the fluid therein.

The present invention is based on the insight that the flow measurementtransducers may as well be used for noise detection purposes: Eventhough the ultrasonic transducers are adapted for flow rate measurementsin the MHz frequency range, they may as well detect noise signals in theHz or kHz ranges. Accordingly, with this embodiment, the ultrasonictransducers of the consumption meters have a dual function, which inturn allows for a simpler construction of the meter compared toembodiments involving a dedicated noise level sensor.

In a particular embodiment of the invention the consumption meter has afirst ultrasonic transducer which is a first piezo-electric transducerwith a first piezo-electric element with a first polarization direction,and a second ultrasonic transducer which is a second piezo-electrictransducer with a second piezo-electric element with a secondpolarisation direction opposite the first polarisation direction.

The application of such oppositely polarised transducers allows for animproved signal-noise-ratio with the detection of noise from the flowtube or the fluid therein.

According to this embodiment, the two piezo-electric transducers havedifferent polarisation directions. Such two transducers, when exposed toan acoustic signal of significantly longer acoustic length than thedistance between the transducers, will observe the same (or nearly thesame) amplitude of the acoustic signal, and in turn display oppositelydirected charge accommodation and oppositely directed currents.Accordingly, the differential signal between the transducers will betwice the signal from each of the transducers, and, as the noise levelis increased only by a factor of √2, resulting in a signal-noise-ratioimprovement of √2.

In this context, a “significantly longer acoustic length” should beunderstood, as the acoustic signal considered should have a wavelengththat is significantly longer than the distance between the transducers.

According to another embodiment of the invention both of the ultrasonictransducers are connected to transimpedance amplifiers of the noisemeasurement sub-circuit.

Thus, according to this embodiment the noise measurement sub-circuitcomprises a first transimpedance amplifier connected to the firstultrasonic transducer for the conversion of a first current indicativeof the noise level of the flow tube or of the fluid therein to a firstvoltage indicative of the noise level of the flow tube or the fluidtherein, and a second transimpedance amplifier connected to the secondultrasonic transducer for the conversion of a second current indicativeof the noise level of the flow tube or of the fluid therein to a secondvoltage indicative of the noise level of the flow tube or the fluidtherein.

As described above, transimpedance amplifiers convert currents intovoltages, thus offering the advantage of eliminating voltage noises.

Further, the noise measurement sub-circuit preferably comprises adifferential amplifier for the amplification of the difference betweenthe first and second voltages indicative of the noise level of the flowtube or the fluid therein to generate the signal indicative of the noiselevel of the flow tube or of the fluid therein.

Thus, for minimization of the interference from electrical noise thenoise measurement sub-circuit may be arranged to receive a differentialsignal from the transducers, the two signals having opposite signs.Thus, the amplifier circuit is symmetrical with respect to the twoinputs in order for cancellation of electrical noise. The differentialmeasurement effectively cancels out electrical interference from theoutside.

As described above, in particular with oppositely polarisedpiezo-electric transducers, the signal-noise-ratio may be improvedconsidering the difference between the transducers signals instead ofeach of the signals individually.

The noise measurement sub-circuit may additionally or alternativelycomprise an operational amplifier with a closed loop feedback, such aswith the closed loop feedback comprising a capacitor in parallel with aresistor, to provide a charge sensitive amplifier.

According to another embodiment of the invention the at least one of thefirst and second ultrasonic transducers comprises a first transducersegment and a second transducer segment, the first transducer segmentbeing operated by the flow measurement sub-circuit to generate thesignal indicative of the flow rate of the fluid, and the second segmentbeing operated by the noise measurement sub-circuit for detection ofacoustic signals of the flow tube or of the fluid therein. Preferably,the first segment is circular and the second segment is annularlyarranged around the first segment.

According to this embodiment the at least one of the first and secondtransducers have different segments dedicated to flow rate measurementand to noise level measurement. The segments may be adapted to therelevant frequency ranges of each of these tasks structurally anddimensionally, such as providing adapted resonance and matching layers.

In terms of frequency, the invention is based on the insight by theinventors, that the most relevant acoustic signals to be detected are inthe frequency range of 10-2000 Hz, preferably in the frequency range of10-1000 Hz, more preferably in the range 10-500 Hz. In particular, thedetection may involve band pass filtering of the acoustic signal such asto remove acoustic signals outside the frequency range 10-500 Hz.

In addition, the present inventors have observed that the abovefrequency ranges apply to different type of flow pipes: They apply tosteel pipes as well as to piping made from polymeric materials.

In case the at least one of the first and second ultrasonic transducersserves as noise level sensor, the flow measurement sub-circuit and thenoise measurement sub-circuit may be arranged in parallel, such as theirrespective operations being selected by a switching means duringnon-overlapping periods.

Moreover, the noise measurement sub-circuit may be switched off from thepiezoelectric transducers when a flow measurement is done. Otherwise,the generation of the ultrasonic signal may be suppressed and the flowmeasurement fail. Furthermore, the switches used should not interferewith the ultrasonic signal as seen by the receiving transducer.

In addition, the noise measurement sub-circuit may be arranged toprocess an output from the sensor for detection of acoustic signals overa period of time, and to accordingly calculate at least one single valueindicative of an average noise level. The sub-circuit may e.g. bearranged to accordingly calculate a plurality of values indicative ofrespective spectral components of average noise level, e.g.corresponding to selected 1/1 octave or ⅓ octave levels etc. Thesub-circuit may alternatively or additionally be arranged to calculate apeak value indicative of a peak noise level for said period of time. Inaddition, the sub-circuit may alternatively or additionally be arrangedto calculate a plurality of different values indicative of noise levelfor said period of time. By measuring over a period of time andprocessing the measured signals, it is possible to reduce the amount ofdata to be communicated from the consumption meter with respect tosensed signals of the flow tube or the fluid therein and which may beconsidered as noise indicative of leakages or other anomalies.

In addition, according to an embodiment of the invention, the generationof the signal indicative of the noise level of the flow tube or of thefluid therein comprises deriving a statistical parameter representingthe noise level.

Still further, the noise measurement sub-circuit may alternatively oradditionally be arranged to calculate a measure of noise level, tocompare said measure of noise level to a threshold value, and togenerate a leakage-warning signal in case said threshold value isexceeded. Especially, in such case, the consumption meter may defersending any noise-related data except in case a leakage warning signalis generated.

The consumption meter preferably comprises a communication modulearranged for communicating said signal indicative of the flow rate ofthe fluid, and for communicating data representing at least one valueindicative of the noise level of the flow tube. The communication modulemay be further arranged to communicate data representing a measured flowrate of fluid in the flow tube or data representing a consumed quantity,such as being arranged to transmit data packets with both a valueindicative of the noise level of the flow tube or the fluid therein, anda value representing a consumed quantity.

The consumption meter may further comprise sensors for measurements ofthe pressure and/or the temperature of the fluid. Further, theconsumption meter may be capable of communicating data representing suchpressure and/or temperature of the fluid via the communication module.

The consumption meter may be a water meter, a gas meter, a heat meter,or a cooling meter. Preferably, the consumption meter is arranged formeasuring consumption data of a supplied utility used as a basis forbilling in which the flow rate measurement forms a part. The consumptionmeter may be used in connection with district heating, district coolingand/or distributed water supply. The consumption meter may be a legalmeter, i.e. a meter which is subdued to regulatory demands. Suchregulatory demands may include demands to the precision of themeasurements.

According to a second aspect, the invention provides a method ofmeasuring a flow rate of a fluid by means of the consumption meteraccording to the first aspect of the invention, the method comprising:operating the first and second ultrasonic transducers by means of theflow measurement sub-circuit to transmit and receive ultrasonic signalsthrough the fluid in the flow tube, generating by means of the flowmeasurement sub-circuit the signal indicative of flow rate of the fluid,operating the dedicated noise level sensor or the at least one of thefirst and second ultrasonic transducers by means of the noisemeasurement sub-circuit to detect acoustic signals of the flow tube orof the fluid therein, and generating by means of the noise measurementsub-circuit the signal indicative of the noise level of the flow tube orof the fluid therein.

With the method, the flow measurement sub-circuit is operated during afirst time period, and the noise measurement sub-circuit is operatedduring a second time period, and wherein the first and second timeperiods are non-overlapping time periods.

Also with the method the dedicated noise level sensor or the at leastone of the first and second ultrasonic transducers is operated by meansof the noise measurement sub-circuit during a period of flow of thefluid in the flow tube below a predetermined flow rate threshold.

According to this embodiment of the invention, noise measurements arepreferably performed during periods of little flow, more preferablyduring periods of no flow at all. During such periods, the noise relatedto the otherwise occurring flow in the fluid piping system, such as flowrelated to the consumers' consumption of fluid, is at a minimum, and anynoise relating to any leakages the more pronounced.

In a third aspect, the invention provides a system comprising aplurality of consumption meters according to the first aspect of theinvention, wherein the plurality of consumption meters are arrangedspatially distributed at consumer sites in a utility network, whereineach of the plurality of consumption meters further comprisescommunication means arranged to transmit data representing the noiselevel of the flow tube or the fluid therein, and wherein the systemcomprises a main collector arranged to receive said data representingthe noise level of the flow tube or the fluid therein from the pluralityof consumption meters.

In particular, the system according to the invention preferablycomprises a data processor arranged to process said data representingthe noise level from the plurality of consumption meters in the utilitynetwork, and to determine a measure of a position of a fluid leakage inthe utility network in response to said data and information regardingindividual positions of each of the plurality of consumption meters inthe utility network.

Whereas the individual consumption meter according the first aspect ofthe invention provides a strong tool for detection of noise related toleakage in a utility network, a system of a plurality of suchconsumption meters distributed at a plurality of consumer sites in theutility network provides an even stronger tool.

It should be understood that noises relating to leakages are often smallcompared to the other noises in the utility network: Noises relating tothe otherwise occurring flow in the network, i.e. the consumers'consumption, as well as other types of noise from the environment, suchas traffic noise and other transient noises, which are as well detectedby the consumption meter.

In particular with little noises from leakages the application of aplurality of consumption meters is advantageous: The noise level isdetected from each of the plurality of consumption meters, i.e. from aplurality of different positions in the network, and the leakageposition may be estimated, such as by known triangular techniques.

In particular, under conditions of limited or even non-flow, the systemof the plurality of consumption meters provides a strong tooldistinguishing between leakage noise and “other” noise sources.

In general, the various aspects of the invention may be combined andcoupled in any way possible within the scope of the invention. These andother aspects, features and/or advantages of the invention will beapparent from and elucidated with reference to the embodiments describedhereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described, by way of example only,with reference to the drawings, in which

FIG. 1 is a schematic illustration of a consumption meter embodimentwith a dedicated noise level sensor transducer,

FIG. 2 is a schematic illustration of a consumption meter embodimentwhere one of the ultrasonic transducers involved in flow ratemeasurements is used to pick up noise,

FIGS. 3a and 3b illustrates a monolithic housing of a consumption meter,wherein a dedicated noise level sensor is arranged at an unbroken flowtube wall,

FIG. 3c illustrates a consumption meter embodiment wherein the dedicatednoise level sensor and the ultrasonic flow transducers are arranged in ahousing mounted on an unbroken flow tube,

FIG. 3d illustrates a consumption meter embodiment wherein the dedicatednoise level sensor and the ultrasonic flow transducers are arranged in asealable housing mounted on flow tube,

FIG. 4 illustrates a segmented ultrasonic transducer to be used with theconsumption meter according to the invention.

FIGS. 5a and 5b illustrate acoustic signals from a steel pipe asrecorded with the consumption meter according to the invention with (a)and without (b) a leak with the pipe, respectively.

FIGS. 6a and 6b illustrate acoustic signals from a plastic pipe asrecorded with the consumption meter according to the invention with (a)and without (b) a leak with the pipe, respectively.

FIG. 7 illustrates an example of a system embodiment where a leak in autility network can be detected from an increase in noise level detectedby a group of consumption meters,

FIG. 8 illustrates for the system of FIG. 7 an example of a leak atanother position in the utility network, and

FIG. 9 illustrates steps of a method embodiment.

DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a consumption meter embodiment wherein two flow transducerT1, T2, in the form of a pair of piezoelectric ultrasonic transducers,are arranged in the wall W of a flow tube in which fluid flows in thedirection indicated by the large arrow to the left. The two transducersT1, T2 are operated by a flow measurement sub-circuit CC1 to transmitand receive ultrasonic signals via the transducers T1, T2, to be able togenerate a flow rate signal indicative of the fluid flow rate, FR basedon known ultrasonic transit time measurement techniques. In the shownembodiment, reflectors R1, R2 serve to direct the ultrasonic signals(dashed arrows) along the fluid flow in the flow tube.

The consumption meter further comprises a dedicated noise level sensorT3 configured for measuring vibro-acoustic signals in the flow tube orof the fluid therein. In the illustrated embodiment the sensor is athird separate transducer T3 located in the flow tube wall between thefirst and second transducers T1, T2. As will be further described in thefollowing other types of sensor may also be used as an alternative tothe transducer. Additionally, in alternative embodiments shown thesensor may be arranged along an unbroken flow tube wall or inside asealable housing adapted to interface with fluid in the flow tube.

Noise in the fluid, indicated by the noise curve in FIG. 1, is capturedby the separate transducer T3. The output from the transducer T3 isapplied to a noise measurement sub-circuit CC2 that processes andoutputs a measure of noise level accordingly. Especially, the thirdtransducer T3 may be a piezoelectric transducer, e.g. similar to thefirst and second piezoelectric transducers T1, T2. Especially, the thirdpiezoelectric transducer T3 may comprise a piezoelectric element, e.g.disc-shaped, with a first surface facing the flow tube, and wherein asecond surface opposite the first surface of the piezoelectric elementis supported by a rigid backing of an acoustically dampening material,such as a dampening material comprising rubber.

The consumption meter preferably comprises a communication module (notshown) arranged to communicate data indicative of the noise level NL inaddition to consumption data based on the measured flow rate FR. In someembodiments, the consumption meter may correlate the measured flow rateFR and the noise level NL (and possibly other measured values) in orderto be able to detect any anomaly, which may then be communicatedaccordingly.

FIG. 2 illustrates a variant of the embodiment of FIG. 1 wherein thefirst piezoelectric transducer T1 involved in the ultrasonic flow ratemeasurement is used as sensor for the acoustic signals in the flow tubeor in the fluid therein.

Thus, in this embodiment, both the flow measurement sub-circuit CC1 andthe noise measurement sub-circuit CC2 are connected to the firsttransducer T1. The first and second sub-circuits CC1, CC2 may beoperated simultaneously, or it may be desirable that they are controlledso that flow rate FR and noise level NL are measured at non-overlappingoperating time periods. However, due to the spectral difference in theacoustic signals to be picked up for detecting leakage or otheranomalies and the ultrasonic signal involved in flow rate measurements(up to 2 kHz versus a few MHz), the second control circuit CC2 may bearranged to spectrally filter the output from the first transducer T1.

Compared to the embodiment of FIG. 1, the embodiment of FIG. 2 save onecomponent, since the first transducer T1 has a dual function. However,in the embodiment of FIG. 1 it may be possible to provide a morededicated transducer T3 that is more sensitive to acoustic signals inthe frequency range relevant for detecting anomalies.

FIG. 3a illustrates a consumption meter embodiment comprising amonolithic housing and flow tube, wherein the dedicated noise levelsensor is arranged at an unbroken flow tube wall together with the firstand second flow transducers T1, T2 for measuring the flow rate. Thehousing and flow tube is cast as a single monolithic component 30providing a housing 300 with an unbroken wall 310 against the flow tube(indicated with arrows).

Referring to FIG. 3 b, the wall 310 includes a first area 320 wherein adedicated noise level sensor in terms of an ultrasonic transducer T3 isarranged. The wall further includes a second area 330 surrounding thefirst area 320. In the shown embodiment, the thickness of the first area320 is smaller than the thickness of the second area. In anotherembodiment (not shown), the thickness of the first area may be equal toare greater than the thickness of the second area. The first areaprovides an acoustic window for the noise level sensor, configured forefficient pick-up of acoustic signals from the flow tube or the fluidtherein.

FIG. 3c illustrates a consumption meter embodiment wherein the dedicatednoise level sensor and the flow transducers are arranged in a housingmounted on an unbroken flow tube. The dedicated noise level censor, suchas an ultrasonic transducer T3, is mounted with a surface facing theflow tube whereby the flow tube provides a coupling surface between thenoise level sensor and fluid flowing in the flow tube. Hereby anon-invasive arrangement is provided and the sensor is protected fromthe fluid in the flow tube.

FIG. 3d illustrates a consumption meter embodiment wherein the dedicatednoise level sensor T3 and the flow transducers T1, T2 are arranged in asealable housing mounted on a flow tube provided with a number ofopenings 311. The sensor and the transducers are mounted in sensorinserts 301 provided in a bottom part of the housing. The sensor inserts301 are protruding cavities constituted by a bottom wall 302 of thehousing. The housing is mounted in a fluid tightly manner on the flowtube, and gaskets or other types of sealing elements (not shown) may beprovided between the housing and the flow tube. When the housing ismounted, the protruding cavities extend into the openings 311 in theflow tube. Hereby the bottom wall of the housing provides a couplingsurface between the noise level sensor and fluid flowing in the flowtube. In an alternative embodiment, the noise level sensor and the flowtransducers may be arranged in one or more common sensor insertsextending into a corresponding number of openings in the flow tube.

The housing 300 is formed as a monolithic entity and the sensor inserts301 are formed monolithically with the housing 300 as protrudingcavities constituting part of the bottom of the housing. The monolithiccup-shaped housing may be cast in a material such a fiber-reinforcedpolymer, e.g. fiber-reinforced polyphenylene sulphide (PPS). The flowtube 310 may be either made from a polymeric material or formed inmetal, such as a brass alloy or stainless steel.

FIG. 4 illustrates a segmented ultrasonic transducer 400 to be used withthe consumption meter according to the invention. The transducer 400 hasa first transducer segment 410, which is a first electrode, and which iscircular and arranged at the centre of the surface of a transducer basearea. In addition, the transducer 400 has a second transducer segment420, which is a second electrode, and which is annular and encirclingthe first transducer segment 410 on the transducer surface. The counterelectrode 430, which is counter electrode for both of the first andsecond electrodes, is arranged at the lateral area of the transducerbody.

The first electrode 410 may be operated by a flow measurementsub-circuit (not shown) for flow measurements, whereas the secondelectrode 420 may be operated by a noise measurement sub-circuit (notshown) for noise measurements.

FIGS. 5a and 5b illustrate acoustic signals from a steel pipe asrecorded with the consumption meter according to the invention with(FIG. 5a ) and without (FIG. 5b ) a leak with the pipe, respectively.

The consumption meter of FIG. 2 was applied onto a 2″ steel pipe, andacoustic signals where recorded in the frequency range 0-1.54 kHz duringa measurement window of 1 second.

A significant acoustic signal is observed below approx. 500 Hz in thecase with the leak (FIG. 5a ), which signal is absent in the absence ofthe leak (FIG. 5b ). This signal indicates the existence of the leak.

FIGS. 6a and 6b illustrate acoustic signals from a plastic pipe asrecorded with consumption meter according to the invention with (FIG. 6a) and without (FIG. 6b ) a leak with the pipe, respectively.

The consumption meter of FIG. 2 was applied onto a 1″ plastic (PEM)pipe, and acoustic signals where recorded in the frequency range 0-1.54kHz during a measurement window of 1 second.

A significant acoustic signal is observed below approx. 500 Hz in thecase with the leak (FIG. 6a ), which signal is absent in the absence ofthe leak (FIG. 6b ). This signal indicates the existence of the leak.

FIG. 7 illustrates a system embodiment, where a plurality of consumptionmeters in terms of water meters W_M are mounted spatially distributed tomeasure water consumed by respective consumers connected to a waterutility network U_N, which all comprise a control circuit arranged tooperate a sensor for detection of acoustic signals of the flow tube,such as described in the foregoing. The water meters W_M all havecommunication means in the form of radio modules capable of transmittingdata representing a noise level of the flow tube in response to thesignal indicative of noise level of the flow tube. Further, the radiomodules are capable of transmitting data representing a consumed amountof water from the utility network U_N. Along with said data, theindividual water meter W_M preferably transmit a unique identificationcode, to allow billing of the individual consumers in accordance withthe consumed amount of water.

A main collector, e.g. located at the utility provider, comprises acommunication module CM arranged to receive said data representing thenoise level of the flow tube from the plurality of water meters, anddata representing a consumed amount of water, preferably along with aunique identification code to identify the individual water meter, whichhas transmitted the data. The noise level data NL_D are provided to adata processor DP, e.g. a server, arranged to monitor said data NL_Drepresenting the noise level from the water meters in the utilitynetwork, and to determine a measure of fluid leakage in the utilitynetwork accordingly. In FIG. 7, a leak is indicated at a specificlocation on the pipe system of the utility network U_N. Stars are usedto indicate water meters where higher than usual noise levels aresensed. The data processor may execute a leakage-monitoring algorithmthat monitors the noise level data NL_D to allow early detection ofleaks. E.g. by comparing observed noise level data NL_D with normallyobserved noise level data NL_D from the same water meters, e.g. inspecific frequency bands, it will be possible to detect increased noisefrom a leak by water meters located near the leak, e.g. the onesindicated in FIG. 7 with stars. This allows the utility provider tolocate a pipe damage and take action at an early stage after a leakagehas occurred.

Based on data representing the noise level from the water meters, thedata processor DP may be arranged to determine a position of a fluidleakage in the utility network U_N in response to said noise level dataNL_D and information regarding individual positions of the consumptionmeters in the utility network. Especially, identification codes allowthe data processor to identify physical positions of the water meters,and by means of applying a triangulation algorithm to the noise leveldata NL_D and the known positions of their origins, the position of apossible leakage may be identified.

FIG. 8 illustrates the same system as in FIG. 7, but for a differentleak position in the pipe system. Again, stars indicate water meterwhere an increase in noise level is sensed, i.e. water meters located inthe pipe system near the leak.

It is to be understood that in such systems, the noise level data NL_Dtransmitted by the water meter may have different complexity, dependingon the amount of processing power in the water meters. E.g., theprocessing power may allow for a calculation of at least one statisticalparameter, which can be transmitted. E.g., a pre-processing in the watermeter may allow the individual water meters themselves to monitor forunusual noises, e.g. by comparing with registered noise levels over along period of time. In such cases, not only noise level data but alsoan alarm signal may be transmitted from the water meter in case apredetermined noise level parameter exceeds a predetermined threshold,e.g. a threshold calculated by the individual water meter in response tonoise levels registered over a long period of time.

It is to be understood that the noise level data NL_D may compriseaverage noise level data, e.g. one overall value, or split up intofrequency bands, e.g. 1/1 octave bands. The noise level data NL_D mayfurther comprise other parameters, such as peak values and/or a levelexceeded in N percent of the time, or still other values determined inresponse to sensed acoustic signals. The noise level data NL_D may betransmitted at regular time intervals, e.g. along with data representinga consumed amount of the utility, and/or the noise level data NL_D maybe requested from the main collector. Especially, it may be desirable tomonitor noise level data NL_D obtained at specific time intervals, e.g.during nighttime, where only few noise disturbing events on the utilitynetwork U_N are expected.

Further, in addition to the noise level data NL_D the data processor maybe arranged to receive further additional measured data from theplurality of water meters, and to take into account such additional datain determining the measure of fluid leakage in the utility networkaccordingly. Such additional data may comprise one or more of: datarepresenting a flow rate, data representing a pressure, datarepresenting a temperature, and the data representing the consumedamount of the utility. As an example, an increased sensitivity toleakages may be obtained, if the data processor is arranged to correlateflow rate data and/or consumed amount of the utility with the noiselevel data NL_D, thereby monitoring for locations with an increase innoise level as well as an increase in a consumed amount of the utilityand/or measured flow rate. Even more data can be used, such as adecrease in pressure, which may further serve as an indicator of aleakage.

FIG. 9 shows an embodiment of a method of measuring a flow rate of afluid supplied in a flow tube by means of a consumption meter. Themethod comprises operating first and second ultrasonic transducersO_T1_T2 by means of a flow measurement sub-circuit to transmit andreceive ultrasonic signals through fluid flowing in a flow tube. Next,generating G_FR by means of the flow measurement sub-circuit a signalindicative of flow rate of the fluid. Next step is operating a dedicatednoise level sensor O_T3 for detection of acoustic signals of the flowtube or the fluid therein by means of a noise measurement sub-circuit.In response, generating G_NL by means of the noise measurementsub-circuit a signal indicative of noise level of the flow tube, andfinally transmitting T_FR_NL by means of a communication module in theconsumption meter data indicative of the flow rate and data indicativeof the noise level of the flow tube. Especially, the flow measurementsub-circuit may operate the first and second ultrasonic transducersduring a first operation time period, and wherein the noise measurementsub-circuit operates the sensor for detection of acoustic signals of theflow tube during a second operation time period. The first and secondoperation time periods may be non-overlapping.

To sum up, the invention provides a consumption meter, e.g. a water orheat meter, for measuring a flow rate of a fluid supplied in a flowtube. First and second ultrasonic transducers are arranged at the flowtube for transmitting and receiving ultrasonic signals transmittedthrough the fluid and operated by a flow measurement sub-circuit forgenerating a signal indicative of the flow rate of the fluid. A noisemeasurement sub-circuit operates a sensor arranged at the flow tube fordetection of acoustic signals of the flow tube, and being arranged togenerate a signal indicative of a noise level of the flow tubeaccordingly. This sensor may comprise a separate transducer, or thesensor may be constituted by one or both of the first and secondultrasonic transducers. The consumption meter may communicate datarepresentative of the noise level via a communication module, along withdata consumed amount of water, heat etc. Such consumer noise levelmeasurement at the consumer site allows collection of noise level datato assist in locating fluid leakages in a fluid supply pipe system.

Although the present invention has been described in connection with thespecified embodiments, it should not be construed as being in any waylimited to the presented examples. The invention can be implemented byany suitable means; and the scope of the present invention is to beinterpreted in the light of the accompanying claim set.

1. A consumption meter arranged to measure a flow rate of a fluid, theconsumption meter comprising: a flow tube with a through-going openingfor passage of the fluid between an inlet and an outlet, first andsecond ultrasonic transducers arranged at a wall of the flow tube fortransmitting and receiving ultrasonic signals transmitted through thefluid, a control circuit comprising a flow measurement sub-circuitarranged to operate the first and second ultrasonic transducers, and togenerate a signal indicative of the flow rate of the fluid from thetransmitted and received ultrasonic signals transmitted through thefluid, wherein the control circuit further comprises a noise measurementsub-circuit, arranged for generating a signal indicative of a noiselevel of the flow tube or of the fluid therein by means of operating adedicated noise level sensor arranged at the wall of the flow tube or bymeans of operating at least one of the first and second ultrasonictransducers to detect acoustic signals of the flow tube or of the fluid.2. The consumption meter according to claim 1, wherein the noisemeasurement sub-circuit is arranged to generate the signal indicative ofthe noise level of the flow tube or of the fluid therein by means ofoperating the dedicated noise level sensor and by means of operating atleast one of the first and second ultrasonic transducers to detectacoustic signals of the flow tube or of the fluid.
 3. The consumptionmeter according to claim 1, wherein the noise measurement sub-circuitcomprises at least one transimpedance amplifier for the conversion of acurrent indicative of the noise level of the flow tube or of the fluidtherein to a voltage indicative of the noise level of the flow tube orthe fluid therein.
 4. The consumption meter according to claim 1,wherein the dedicated noise level sensor is arranged at an acousticwindow provided as an integrated part of the wall of the flow tube. 5.The consumption meter according to claim 4, wherein the consumptionmeter comprises an integrated housing and flow tube in the form of amonolithic polymer structure cast in one piece and having a cavity, thecavity accommodating the first and second ultrasonic transducers and thecontrol circuit, and wherein the flow tube wall with the acoustic windowis unbroken.
 6. The consumption meter according to claim 4, wherein theacoustic window is constituted by a first area of the flow tube wall ofreduced thickness, compared to a second area of the flow tube walladjacent the first area.
 7. The consumption meter according to claim 1,wherein flow tube is provided with one or more openings, and theconsumption meter further comprises a housing mounted on the flow tube,and wherein the dedicated noise level sensor is arranged at a bottomwall of the housing arranged in an opening in the flow tube wall.
 8. Theconsumption meter according to claim 7, wherein the bottom wall of thehousing provides a protruding cavity constituting a sensor insertextending into the opening in the flow tube wall, and wherein thededicated noise level sensor is arranged in the sensor insert. 9.(canceled)
 10. The consumption meter according to claim 4, wherein thededicated noise level sensor is a piezo-electric sensor.
 11. (canceled)12. The consumption meter according to claim 1, wherein both of thefirst and second ultrasonic transducers are operated to detect theacoustic signals of the flow tube or of the fluid therein.
 13. Theconsumption meter according to claim 12, wherein the first ultrasonictransducer is a first piezo-electric transducer comprising a firstpiezo-electric element with a first polarization direction, and whereinthe second ultrasonic transducer is a second piezo-electric transducercomprising a second piezo-electric element with a second polarisationdirection opposite the first polarisation direction.
 14. The consumptionmeter according to claim 12, wherein the noise measurement sub-circuitcomprises a first transimpedance amplifier connected to the firstultrasonic transducer for the conversion of a first current indicativeof the noise level of the flow tube or of the fluid therein to a firstvoltage indicative of the noise level of the flow tube or the fluidtherein, and a second transimpedance amplifier connected to the secondultrasonic transducer for the conversion of a second current indicativeof the noise level of the flow tube or of the fluid therein to a secondvoltage indicative of the noise level of the flow tube or the fluidtherein.
 15. The consumption meter according to claim 14, wherein thenoise measurement sub-circuit further comprises a differential amplifierfor the amplification of the difference between the first and secondvoltages indicative of the noise level of the flow tube or the fluidtherein to generate the signal indicative of the noise level of the flowtube or of the fluid therein.
 16. The consumption meter according toclaim 12, wherein the at least one of the first and second ultrasonictransducers comprises a first transducer segment and a second transducersegment, the first transducer segment being operated by the flowmeasurement sub-circuit to generate the signal indicative of the flowrate of the fluid, and the second segment being operated by the noisemeasurement sub-circuit for detection of acoustic signals of the flowtube or of the fluid therein.
 17. The consumption meter according toclaim 16, wherein the first segment is circular and the second segmentis annularly arranged around the first segment.
 18. The consumptionmeter according to claim 1, wherein the acoustic signals detected are inthe frequency range of 10-2000 Hz, preferably in the frequency range of10-1000 Hz, more preferably in the range 10-500 Hz.
 19. The consumptionmeter according to claim 1, wherein the generation of the signalindicative of the noise level of the flow tube or of the fluid thereincomprises band pass filtering of the acoustic signal to remove acousticsignals outside the frequency range 10-500 Hz.
 20. (canceled) 21.(canceled)
 22. (canceled)
 23. A method of measuring a flow rate of afluid by means of a consumption meter according to claim 1, the methodcomprising: operating the first and second ultrasonic transducers bymeans of the flow measurement sub-circuit to transmit and receiveultrasonic signals through the fluid in the flow tube, generating bymeans of the flow measurement sub-circuit the signal indicative of flowrate of the fluid, operating the dedicated noise level sensor or the atleast one of the first and second ultrasonic transducers by means of thenoise measurement sub-circuit to detect acoustic signals of the flowtube or of the fluid therein, and generating by means of the noisemeasurement sub-circuit the signal indicative of the noise level of theflow tube or of the fluid therein.
 24. The method according to claim 23,wherein the flow measurement sub-circuit is operated during a first timeperiod, and the noise measurement sub-circuit is operated during asecond time period, and wherein the first and second time periods arenon-overlapping time periods.
 25. (canceled)
 26. A system comprising aplurality of consumption meters according to claim 1, wherein theplurality of consumption meters are arranged spatially distributed atconsumer sites in a utility network, wherein each of the plurality ofconsumption meters further comprises: communication means arranged totransmit data representing the noise level of the flow tube or the fluidtherein, wherein the system includes a main collector arranged toreceive said data representing the noise level of the flow tube or thefluid therein from the plurality of consumption meters, and a dataprocessor arranged to process said data representing the noise levelfrom the plurality of consumption meters in the utility network, todetermine a measure of a position of a fluid leakage in the utilitynetwork in response to said data and information regarding individualpositions of each of the plurality of consumption meters in the utilitynetwork.
 27. (canceled)